1. Field of the Invention
The present invention relates in general to delaying the opening of parachute canopies and, more particularly, to a slider type reefing device that is secured to the canopy during initial parachute deployment.
2. Description of the Related Art
A known problem with the use of parachutes to lower personnel and unmanned cargo to the ground from airplanes and other airborne craft is the sudden shock when the parachute opens and fills quickly with air. This is especially serious at high speeds where the canopy fills more rapidly, as may occur during the deployment of parafoils designed to fly at high wing loadings.
The mechanical reefing of parachute canopies by sliders on the canopy suspension lines for the purpose of delaying canopy opening and/or reducing canopy opening shock is already well known as representatively disclosed in U.S. Pat. No. 5,005,785 to Puskas. According to such prior art arrangement, opening of a ram-air inflated, airfoil gliding parachute canopy (hereinafter “ram air parachutes” or “ram air canopies”) is physically restricted to a decreasing extent as the reefing slider is displaced downwardly from an upper reefing position along converging suspension lines under canopy opening forces.
The reefing system disclosed in the Puskas patent achieves aerodynamic delay by means of a flow deflecting flap extending from the slider beyond the suspension lines so as to be positioned in alignment with the leading edge portion of the canopy in the upper reefing position. However, because the slider is not physically connected to the canopy, heavier payloads can render the flap insufficient to withstand the force of the air flowing into the canopy upon deployment. Hence, under heavy loading of the parachute canopy, the slider may descend too rapidly such that adequate retarding of the canopy opening process is not achieved.
One system has been developed by Pioneer Aerospace Corporation that is directed to a large forward-gliding parachute canopy bearing a heavy payload such as spacecraft returning from orbit. This system relies upon pyrotechnic connections between adjacent chords of the canopy which are activated to release one section of the canopy at a time. However, the system is highly complex and very expensive, making it unsuitable for routine and repeated airborne delivery of equipment and supplies such as is needed for troop support during military operations, particularly during periods of war and foreign occupation.
Therefore, a need exists for a reefing device suitable for large and very large ram air canopies that produces a retarded rate of slider descent while also providing suspension line management capabilities. A need also exists for a reefing device that is released based upon actual forces imposed on the canopy, making it more responsive to dynamic deployment or opening conditions and appropriate for use with heavy payloads being delivered by forward gliding parachute canopies of the ram-air inflated airfoil type.